Melody or cphill plz help

I rarely if ever answer questions that have not been asked properly, all those $ signs have no meaning.

Plus you will have a slightly higher chance of getting good answers if you become a member. (it is free and easy) 

If you make a good impression as a member it becomes almost a given that you will get a good answer.

$ab^4 = 384\\ a^2 b^5 = 4608$

Considering the second equation: 

$ab^4 \cdot ab = 4608\\ ab = \dfrac{4608}{384} = 12$

Considering the first equation:

$ab^4 = 384\\ ab\cdot b^3 = 384\\ b = \sqrt[3]{\dfrac{384}{12}} = 2\sqrt[3]4$

Substituting directly gives $a =3 \sqrt[3]{2}$